This invention relates generally to dryer systems, and, more particularly, to control systems for clothes dryers.
An appliance for drying articles such as a clothes dryer for drying clothing articles typically includes a cabinet including a rotating drum for tumbling clothes and laundry articles therein. One or more heating elements heats air prior to air entering the drum, and the warm air is circulated through the air as the clothes are tumbled to remove moisture from laundry articles in the drum. See, for example, U.S. Pat. No. 6,141,887.
Typically, such an appliance is operated for a set a drying time for drying the clothing articles therein. For the duration of the set time, the heating elements are activated and deactivated to maintain warm air circulation inside the drum, and for more accurate control of the dryer heating elements, a temperature sensor is sometimes used in conjunction with the heating elements. Rather than turning the heaters on and off for specified times, the heating elements can be operated more or less on demand for precise temperature control while minimizing energy consumption.
To prevent excessive temperatures in the drum, thermostat switches are also employed to deactivate the heating elements when the temperature of the circulated air reaches a predetermined threshold. A small heating element is sometimes placed adjacent the thermostat to provide a thermal bias. The provision of a thermal bias causes the thermostat to operate at a lower air temperature and is commonly used to lower the maximum exhaust air temperature at which the operating thermostat reacts. See, for example, U.S. Pat. No. 4,842,1 92.
It has been observed, however, that the thermostat switches can sometimes interfere with the temperature sensor control of the heating elements. Laundry loads, especially larger ones, may greatly restrict the airflow in the drum, which, in turn, may cause a safety thermostat to deactivate one or more of the dryer heaters before the temperature sensor indicates that the heaters should be deactivated. Thus, the thermostat prematurely deactivates the heaters and extends drying time, thereby negatively impacting dryer performance.
In one aspect, a control system for a clothes dryer including a temperature sensor and a thermostat for regulating at least one dryer heating element is provided. The control system comprises a microcomputer programmed to compensate for a conflict between the thermostat temperature regulation and the temperature sensor temperature regulation during dryer operation at a selected operating temperature.
In another aspect, a control system for regulating activation and deactivation of heating elements in a clothes dryer is provided. The control system comprises a temperature sensor in communication with a heated air source, a thermostat in communication with the heating air source and operatively coupled to the heating elements, and a microcomputer operatively coupled to said temperature sensor and to the dryer heating elements. The microcomputer is configured to compensate for premature deactivation of the heating elements during operation of the dryer.
In another aspect, a clothes dryer is provided. The dryer comprises a cabinet, a rotatable drum mounted in said cabinet, a drive system for rotating said drum, an air circulation system, a temperature sensor in communication with said air circulation system, a thermostat in communication with said air circulation system, and at least one heating element in communication with said air circulation system and operatively coupled to said thermostat. A controller is operatively coupled to said temperature sensor and to said heating element, and the controller is configured to activate and deactivate said heating element in response to an output from said temperature sensor to regulate air circulation temperature between an upper and lower bound. The controller is further configured to compensate for deactivation of said heater element before said upper bound has been reached.
In another aspect, a method of operating a clothes dryer including a microcomputer, a temperature sensor, and a thermostat for regulating a temperature of air circulating in the dryer is provided. The method comprises determining when the thermostat is interfering with temperature regulation via the temperature sensor, and adjusting setpoints of the temperature sensor when the thermostat is interfering with temperature regulation via the temperature sensor.
In still another aspect, a method of operating a clothes dryer is provided. The dryer includes a microcomputer, a temperature sensor, and a thermostat for regulating a temperature of air circulating in the dryer by activating and deactivating at least one heating element. The method comprises regulating activation of the heating element in response to temperature feedback from the temperature sensor, monitoring circulation air temperature over a period of time when the heating element is activated in response to feedback from the temperature sensor, determining whether the air circulation temperature decreases by a predetermined amount within the predetermined time, and adjusting an operating setpoint of the temperature sensor when the air circulation temperature decreases by the predetermined amount within the predetermined time.